1. Field of the Invention
This invention is directed to a diagnostic system for a rotating electrical apparatus, and more particularly to an online system for diagnosing the condition and maintenance requirements of an operational motor.
2. Background of Information
Large motors require periodic preventive maintenance to ensure reliable and efficient performance over an operational lifetime. The requisite maintenance period is a function of a specific design of a particular motor. Reactor coolant pump (RCP) motors used in nuclear power plants, for example, are typically inspected annually, during refueling outages, and are disassembled for inspection or refurbishment every five to ten years. Significant time and field effort are required to disassemble such motors and perform the requisite inspections.
A set of motors having an identical design are, nevertheless, different in terms of a variety of factors such as normal manufacturing tolerances, operating history and environment, and quality of maintenance. A pre-specified operating period, before motor inspection or maintenance, is an informed estimate of the appropriate operational schedule for a typical motor under recommended operating conditions. In some cases, the pre-specified operating period may be too long (e.g., where recommended motor operating parameters have been exceeded) and, hence, inefficient operation may result at the end of the period. In other cases, the prespecified operating period may be too short (e.g., where the motor has been relatively lightly loaded) and, therefore, unnecessary costs associated with outage time, manpower and material will be expended. Furthermore, where a RCP motor is located within a nuclear containment vessel, unnecessary human exposure to radiation would result.
There is a need, therefore, for a system which accurately diagnoses the condition of an operational rotating electrical apparatus.
There is a more particular need for such a system which accurately diagnoses the maintenance or inspection requirements of the operational rotating electrical apparatus.